For example, a fuel filter device is provided in a fuel supply unit, which is provided between a fuel tank and a fuel injection pump for supplying fuel into a diesel engine or the like. The fuel filter device is configured to capture an organic foreign substance such as dust or an inorganic foreign substance such as metal in fuel, for example. The fuel filter device includes a filter element formed from a filter material for capturing the foreign substance in fuel.
A fuel filter device may include an additional component having a predetermined function to cope with a predetermined fuel environment. For example, according to JP-A-2006-105092, a fuel filter device is provided with a metal ion capturing material as the additional component for capturing metal ions in fuel, which cannot be substantially captured by the filter element. JP-A-2006-105092 discloses a configuration where the metal ion capturing material is inserted between two filter elements, which are collectively accommodated in a case.
While description is not made in JP-A-2006-105092, a metal ion capturing material is reduced in capturing capability after use. The metal ion capturing material reduced in capturing capability needs to be removed from the case, and a new or degenerated metal ion capturing material needs to be loaded into the case. However, in the structure of JP-A-2006-105092, the metal ion capturing material is inserted between the two filter elements. Therefore, the metal ion capturing material needs to be removed from the case together with filter elements being not necessary to be removed, and another metal ion capturing material needs to be loaded into the case together with different filter elements. That is, the metal ion capturing material cannot be easily loaded into and removed from the fuel filter device independently of the filter elements. Such a problem lies not only in the metal ion capturing material, but also lies in a component such as an auxiliary filter element for capturing particulate matters having a larger diameter than a diameter of particulate matters that can be captured by a filter element.